1. Field of the Invention
The present invention relates to a method and appratus for determining the material flow rate of bulk material, transported by belt conveyers or the like, by continuously determining the contours of the free surface of the bulk material, at right angles to the direction of transport, by means of continuous non-contact distance measurement using at least one transmitter-receiver mechanism coupled with a computer, and by computing the bulk material cross section.
2. Description of the Prior Art
It is already known to measure the flow of bulk materials transported by belt conveyers by determining the contours of the free surface of the bulk material using a photographic camera or a television camera, or by ultrasonic distance measurement. Taking into consideration the known profile, which is determined at the measuring point by the set of supporting idler rollers and the conveyer belt, the bulk material cross section is then determined at relatively short intervals and is multiplied by the transport speed to yield the volumetric flow, i.e. the volume transported per unit of time. The flow rate is found by multiplying the density of the bulk material. To simplify matters, both volumetric flow and material flow will be designated here summarily as material flow rate.
In a method of the type described above, where the continuous distance measurement is carried out without any physical contact with the assistance of at least one transmitter-receiver mechanism, the latter consists of an ultrasonic distance-measuring device. However, this known method suffers from the drawback that it is necessary to install the ultrasonic distance-measuring device in close proximity to the bulk material surface, so that the sound impact footprint surface area, which is formed by the so-called sound lobe (beam), is not too large; so that the reflected sound pulse still has sufficient energy to provide an unequivocal value (reading), this being particularly applicable to materials with poor reflectivity; and so that air streams which will cause disturbances can be positively screened off. The installation of the measuring devices in the vicinity of the surface of the bulk materials can, however, easily lead to the destruction of the distance-measuring devices, particularly in the area of transfer points. Even if the measuring devices are installed relatively close to the surface of the bulk material, measuring errors frequently result because of various influences, particularly in the case of higher transporting velocities.
It is an object of the present invention to provide a method, and an apparatus for the implementation of the method, which will make it possible to achieve accurate measured values even in the case of greater measuring distances and at the same time in the case of greater transporting velocities.